Fair Value Measurements - MEC - Level 3 (Details) - Derivative [Member] - MidAmerican Energy Company [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (1)	$ (1)	$ 3	$ (2)
Changes in fair value recognized in net regulatory assets	(1)	(2)	(4)	(2)
Settlements	1	1	0	2
Ending balance	$ (1)	$ (2)	$ (1)	$ (2)